MetService keeping an eye on two tropical disturbances in Pacific

Friday, 7 April 2017

Northwest of Fiji, this is one of two tropical disturbances being monitored in the Pacific.

There are no tropical cyclone warnings for the South Pacific, the MetService says.

Online forecasting and some media reported a new tropical cyclone warning for New Zealand.

Edgecumbe was inundated when a stopbank failed and the township flooded.

There are none at present.

There are, however, several separate weather systems in the vicinity of New Zealand - a low pressure system forming to the west of the country, and two tropical disturbances in the south Pacific.

Those disturbances - too diffuse to be defined as cyclones - are east of Tonga near Niue and northwest of Fiji.

**READ MORE:

* Another wet week for most of the NI

A composite satellite image showing the ex-cyclone to the east of New Zealand. A tropical disturbance can be seen at top left; another tropical disturbance can be seen to the upper right.

* 'Exceptional' cluster of five downpours**

A MetService tropical cyclone bulletin says the chance of the system near Niue intensifying into a tropical cyclone is low to moderate over the weekend but, as a significant tropical depression, it is expected to bring heavy rain.

New Zealand on Friday in a satellite image.

The other tropical disturbance is expected to move south-southwest towards southern Vanuatu on Sunday and Monday.

MetService forecaster Matt Ford said there were two tropical disturbances being monitored by the Fiji authorities.

A tropical disturbance near Fiji in the south Pacific on Friday. New Caledonia is near the centre.

'Neither of them are tropical cyclones at the moment but they are promising conditions.

'Possibly the one that is getting everybody's knickers in a twist is tropical disturbance 20F [near Fiji moving towards Vanuatu].

Edgecumbe flooded after ex-Cyclone Debbie merged with a low pressure system and dumped a month's worth of rain in a couple of days.

'There are no tropical cyclones. To the northeast of Vanuatu it looks like it will move towards Vanuatu and it's likely it will reach strength.

'What happens to it after…we're really talking about Easter weekend. This weekend it's likely to move across Vanuatu.

'Around Monday or Tuesday it's deciding what to do. There's quite a range of possibilities and outlooks at this time. We're looking at various computer models and guidelines. Those kinds of possible forecast outcomes can change.

'There are massive amounts of uncertainty when it moves out of the tropics.

'There's a possible scenario which brings it towards New Zealand. The story is what's going to happen to Vanuatu.

'We're keeping an eye on it next week.'

Ford said there was another low pressure system moving across the Tasman towards New Zealand.

This system was expected to bring some heavy rain next week.

The Fiji Meteorological Service tropical cyclone forecast largely echoes the New Zealand meteorologists.

Strong winds, heavy rain, and thunderstorms are forecast for Niue over the weekend.

Meanwhile, the National Institute of Water and Atmospheric Research says Auckland recorded the equivalent of normal April rainfall - 84.6mm - in 14 hours from Tuesday evening to Wednesday morning.

Many parts of the country had two or three times the normal April monthly rainfall in just two or three days.

Hamilton had its second wettest start to any calendar year on record since 1907 with 537 mm of rain.

The torrent dumped 164mm of rain on Tauranga while Whakatane had its wettest April day on record since 1952.

Kaitaia has its second wettest start to any calendar year on record since 1948 with 567 mm.

Wellington Airport recorded 72 mm in one day between 9.00am Wednesday and 9.00am Thursday, making it the wettest day at the airport in almost a decade.

The Niwa forecast said the country was stuck in a pattern favouring low pressure systems to the west and sweeping high pressure to the south and east.

Niwa forecaster Ben Noll said another band of heavy rain was expected on Tuesday for the North Island and north and east of the South Island.

'Furthermore, a tropical disturbance north of Vanuatu is being monitored for strengthening over the weekend into early next week.

'There is some uncertainty regarding the eventual strength and track of the tropical system, although its progress will need to be watched closely as it could influence New Zealand's weather later next week,' he said.

However, Philip Duncan, forecaster for Weather Watch, said looking at the international models, two tropical cyclones may be forming north of New Zealand next week.

He was fairly confident that one of these would not reach the New Zealand's shores, but the other might directly impact the North Island.

'That's the sort of disclaimer with a long-range forecast like this. The models can change, and they do change, and we're not locking this in yet.'

An ex-cyclone would bring with it tropical moisture, and tropical instability, he said.

'The combined concern is that the Tasman low sucks down the cyclone and you end up with a bit of a double whammy, and that's a possibility.'

Even though it's not a certainty, with rivers already full, and the ground saturated, Duncan said people might want to be prepared.

'The entire North Island is now wetter than average, and two months ago the entire North Island was in drought.'